Sound damper



June 7, 1927. 1,631,924

7 H. w. K. Eii-QEY S OUND DAMP ER Filed June 18, 1924 Patented June 7,1927.

UNITED STATES ?ATENT GFFICE.

HEINRICH WILLEM: KAREL DE BREE, OF THE HAGUE, NETHERLANDS.

SOUND DAMPER.

Application filed June 18, 1924. Serial No. 720,859.

The object of my invention is to provide improved means for absorbing oreliminating accidental or parasitic sound and thereby increase thetonical clarity in the transmission or amplification of reproduced soundthrough an'iplitying horns, tone arms, sound chambers as used in conection with the socalled hornless type of cabinet graniophones, loudtalkers and any other more or less tubular transmitting elementssuitable for this purpose, irrespective of whether the sound isreproduced by mechanical, electrical or other instrumentalities.

The accidental orparasitic sound may originate from the propervibrations of a diaphragm or other sound transmitting parts, from thescratching of the stylus needle or diamond over the record of talkingmachines or from other sources, but whatever its source may be, its wavelengths are, as a rule, appreciably different from those of the soundwhich it is desired to convey, and I have now discovered that owing tosaid dilference in wave lengths it is possible to remedy the said detectin a very simple manner by separating the disturbing lre quencies fromthe others and absorbing them more or less tully. This result isobtained by the provision, within the horn or other more or less tubularsound transmitting element, of a member, or a plurality of memhere forbreaking the undesired sound waves, said member being so arranged andconstructed as to check or hamper and also absorb or mutlie theundesired vibrations while allowing the other frequencies to pass Anessential feature of my novel sound improver is, that it clears thecentral portion of the horn or the like, as contradistiuguished fromknown means such as a ball like member disposed centrally within thehorn at an adjustable distance from the neck and serving only forcontrolling the intensity of the sound. another important feature of myinvention being that the sound improver is in perfect contact with theinner wall ol? the horn or the like through only part of thecircumference thereo'l. In practice it has been found that verysatisfactory results are obtained by the en'iployment ot a soundiinprover which extends through one half to three quarters of theinterior circumference of the horn, leaving the balance unobstructed.

My novel sound improver is made of a suitable sound damping materialsuch as rubber, felt, fabric, etc, and is so formed that the undesiredsound waves, which are propagated along that portion oi? the wall of thesound transmitting element where the sound improver is placed, cannotcontinue their paths over the iniprover, or between the latter and thewall, but are actually checked. For this purpose the front :tace of theabsorber may be concave, or convex, or have another suitable form.

In order that my novel sound improver may be in perfect contact with theinner wall of the horn, it may be pasted thereto, or sunk thereinto, orheld in place in any other suitable manner at the required distance fromthe month, said distance depending, inter alia, upon the construct-ionot' the horn or the like and the character of the sound to be conveyed.Preferably, however, I use a loose improver adapted by its ownresiliency, or by the resiliency oil a s' u-iug, to be firmly pressedagainst the inner wall of the horn, as this has the advantage that i candetermine where the in'iprover should be located to have the best effectin the reproduction oli a given record or the amplification or a givenvoice. As a rule it will be found that with a gramophone horn o'tconvel'itional configuration the best results are obtained when theiinprover is placed in the neck r the portion contiguous therewith.

The annexed drawing illustrates, by way of example only, a soundiniprover in accordance with my invention, Fig. i being a longitudinalsection, and F g. 2 a cross section on a reduced scale of the iinprovertitted in the neck of a sound anipli tying horn of conventional form.

The improver shown in Fig. l simply consists ot a spring blade 3,wrapped around the central portion of which is a rope oi? flannel lforming a pad of sound absorbing material, and t] c ends of the blade 3are bent into hooks 5 as shown. .lt will be understood. that, when lforce the ends of the spring blade towards one another between myfingers l can introduce the improver into an amplifying horn {3 and putit into place and that, when 1 release the spring, the pad l is firmlypressed against the inner wall through part of the circlun'l ereuce oithe horn, thereby positively checking the undesired sound waves. Itnecessary. I can then simply push the iniprovcr further inward oroutward as circumstances require, and

thus cause the improver to occupy a greater or a smaller portion of theinner circumference of the horn.

What I claim is 1. In combination with-a sound transmitting element, ofmeans arranged in said velement and in contact with the inner suri'aceof the wall thereol' throughout substantially its full length, saidmeans having a length approximating one-half the cylindrical length ofthe wall at the point of application of the means and extending inwardlyfrom the inner surface of said wall to provide throughout; its length acomplete interruption to the passage of sound waves.

2. In combination with a tubular sound transmitting element otadampening memher in solid form adapted to be held in contact with theinner. surface of the element throughout substantially its full lengthand extending substantially one-half the cylin drical length of suchwall at the point of application, said dampening member interposing a.direct barrier to the passage 01" sound waves throughout its length andthickness.

3. In combination with a tubular sound. transmitting element, of a solidsubstan tially cylindrical dampening member engaging the inner surfaceof the element and extending throughout approximately onehalf thecylindrical length of the wall at the point of application, saiddampening memher being of a thickness radially of the member less thanthe radius of such member, whereby to interpose a solid barrier to thesound waves throughout an area having a circumferential lengthapproximately onehalf the circular length of the element and a thicknessless than the radius of the element, the central portion of the elementand the remaining area of the all surface thereof being completelyunobstructed.

.4. A dampening barrier for sound waves passing through a tubulartransmitting element, comprising a substantially cylindrical memberconstructed solidly of dampening material and having a lengthapproximating one-half the cylindrical length of the element at thepoint at which said member is to be placed, the thickness of the memberbeing less than the radius of the element at v the point of applicationof the member.

The combination with a tubular sound transmitting element. of adampening member of solid formation having a length approximately equalto one-half the circumferential length of the element at the point ofapplication of the member, and means carried by the member forresiliently holding the same in contact with the inner surface of theelement at the point of application.

In testimony whereof I affix my signature.

HEINRICH WILLEM KARI-1L de BREY

